This invention relates to an automatic sphygmomanometer having an internal pneumatic pump used in pressurizing a cuff wrapped around an arm of a patient when measuring blood pressure.
1. Field of the Invention
In conventional automatic sphygmomanometers having a pneumatic pump, the pump produces noise and vibration when operating. In hospital rooms where silence is required, the use of such a sphygmomanometer poses problems. In particular, it is normally desired that a patient be in a calm mental condition when undergoing a blood pressure measurement. This requires that care be taken to prevent noise and vibration that might otherwise agitate the patient.
To reduce vibration produced by the pneumatic pump during operation, a conventional approach is to support the pump by means such as a rubber vibration insulator. However, since the rubber vibration insulator is in mechanical contact with the pump and is itself mechanically joined to the case of the sphygmomanometer, pump vibration is diminished in dependence solely upon the damping factor of the rubber. In particular, since a sphygmomanometer has an overall weight of about 1 kg, it is not possible with the conventional arrangement to absorb the vibration energy because of the mass of the sphygmomanometer, and it is possible that the entire sphygmomanometer may resonate due to the vibration set up by the pump.
Another disadvantage with the conventional automatic sphygmomanometers is that measures for preventing leakage of noise produced by the pneumatic pump during operation are unsatisfactory. Since noise and vibration can cause anxiety in a patient undergoing a blood pressure measurement, the measured values of blood pressure are apt to be abnormal because of these external stimuli. This obviously is an unsatisfactory situation.